JPH0645465B2 - Method for manufacturing optical glass element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the production of highly accurate optical glass elements such as lenses and prisms, and optical glass elements such as an optical glass molded body of a material for reheat press molding of the optical glass element. Regarding the method.

2. Description of the Related Art In recent years, optical glass lenses are in the direction of aspherical surface that can achieve both simplification of the lens structure of optical equipment and weight reduction of the lens portion at the same time. In manufacturing this aspherical lens, it is difficult to process and mass-produce it by a conventional polishing method which is a method of manufacturing an optical lens, and a molding method using a mold is considered promising.

The molding method using this mold is that aluminum hydroxide is applied on the mold that has been finished to the desired surface quality and surface accuracy in advance,
This is a method in which a lump of optical glass is heat-molded or a lump of optical glass in a molten state is heat-molded in a state where a release agent such as magnesium carbonate or carbon is applied or covered. (For example, Japanese Patent Publication No. 54-6031
(2) The problem to be solved by the invention In the case of an optical glass element such as an aspherical lens or a prism, it is required to have a surface free from defects or release agent, surface roughness, and surface accuracy. The optical glass element and the optical glass molded body of the reheat press molding material for the optical glass element have become very expensive.

That is, there is no defect on the surface of the optical glass molded body (for example, mirror surface state with surface roughness RMS of 0.005 micron or less).
In order to achieve this, it is necessary to perform a polishing or etching treatment, and the optical glass molded body is expensive, and it has been strongly desired to develop a method capable of producing a highly accurate optical glass molded body at low cost.

Means for Solving the Problems In order to solve the above problems, the present invention produces a glass cob by receiving molten glass in a non-oxidizing atmosphere with a first heat processing jig that does not have a shape similar to that of a desired optical glass element. A step of inverting and replacing the glass gob and the second heat processing jig in a state where the glass gob is bonded to a second heat processing jig having a similar shape to a desired optical glass element, A method for producing an optical glass element, which comprises a step of producing an optical glass molded body by the surface tension of the glass gob that is heat-softened by a heat processing jig, and a step of heating and pressing the optical glass molded body with a press molding die. It is provided.

Action Since high-temperature molten glass is in a chemically extremely active state, it caused a great deal of damage to the heat processing jig and reacted or fused with the optical glass. In order to prevent this, it is effective to use the heat processing jig without heating it, but large wrinkle-shaped defects due to heat shrinkage occur on the contact surface of the glass gob in contact with the heat processing jig. On the other hand, the surface of the glass gob not in contact with the heat processing jig was a very smooth surface.

In order to remove wrinkle-like defects on the surface of the glass gob in contact with the heat processing jig, after receiving the molten glass with the first heat processing jig that does not have a shape similar to the desired optical glass element, the desired surface of the glass gob is desired. The glass gob is adhered to the second heat processing jig by bringing the optical glass element and the second heat processing jig having a similar shape into contact with each other. With the glass gob attached to the second thermal processing jig, reverse the second thermal processing jig to stably replace the glass gob from the first thermal processing jig to the second thermal processing jig, The glass gob having a wrinkled surface facing upward is largely deformed by the surface tension of the glass by the heated second heat processing jig.
Furthermore, the optical glass element having no surface defects can be manufactured by subjecting this optical glass molded article to heat and pressure molding with a press molding die.

For the first heat processing jig that directly receives the molten glass, a material having poor wettability with the molten glass and excellent releasability, such as carbon, boron nitride, aluminum nitride, chromium nitride, and stainless steel, is suitable. There is. The thin film that covers the second heat-processing jig and the press-molding die is a simple substance of noble metal, tungsten, tantalum, rhenium, or hafnium that reacts with or slightly adheres to the optical glass in a non-oxidizing atmosphere, or their An alloy is desirable.

In the present invention, the non-oxidizing atmosphere in which the optical glass and these thin films do not react or fuse with each other is an inert gas such as nitrogen, argon or helium, and hydrogen or carbon monoxide or carbon dioxide in these inert gases. Carbon oxides, hydrocarbons such as methane, ethane, ethylene and toluene, halogenated hydrocarbons such as trichloroethylene and trichlorotrifluoroethane, alcohols such as ethylene glycol and glycerin, fluorocarbons such as F-113 and F-11 It is a mixture of types.

These atmospheres are appropriately selected depending on the conditions such as the optical glass composition, the thin film composition to be coated on the thermal processing jig, the temperature and time of thermal deformation, the temperature and time of press molding, the shape of the optical glass molded body and the like.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 is a sectional view of a first heat processing jig, a second heat processing jig and a press molding die used in the present invention. Carbon was used as the first heat processing jig and processed into a flat shape. Cemented carbide (WC-5TiC) as the base material of the second heat processing jig
Concave optical surface 1 with a radius of curvature of 15 mm using -8Co)
Was formed. The optical surface 1 was further lapped with ultrafine diamond powder to make it a mirror surface having a surface roughness (RMS) of about 30Å in the first hour. A thin film 2 of platinum-iridium-osmium alloy (Pt-It-Os) was coated on the mirror-finished surface of the heat processing jig by a sputtering method.
As with the second heat processing jig, cemented carbide (WC-
5TiC-8Co) is used to form a concave optical surface 1 having a radius of curvature of 20 mm, and a platinum-iridium-osmium alloy (Pt-Ir-Os) thin film 2 is coated by sputtering.
The mold was used for press molding.

As the molten glass 14, 30% by weight of silica (SiO ₂ ), 50% by weight of barium oxide (BaO), 15% by weight of boric acid (B ₂ O ₃ ), and barium borosilicate glass having the balance of trace components were used. After melting this glass at 1200 ° C., about 3 g of molten glass 14 was passed through the nozzle 12 kept at 800 ° C. and nitrogen gas 2
First heat processing jig 24 held in a molding machine in an atmosphere mixed with 0 liter / min and hydrogen gas 2 liter / min.
Was added dropwise. The first heat processing jig 24 is heated to 200 ° C. in advance, and immediately after the dropping, the second heat processing jig 16 is melted in the molten glass 14 and the molten glass 14 is transferred to the second heat processing jig 16. Attached. The second heat processing jig 16 having the molten glass 14 attached thereto was inverted by the arm 25, and the molten glass 14 was replaced with the second heat processing jig 16 as shown in FIG. After being thermally deformed by the second heat processing jig 16 at 630 ° C. for 10 minutes, it was press-molded by the press-molding die 20. Press molding conditions are mold temperature 560 ° C, press pressure 3
It was 0 Kg / cm ² and the pressing time was 2 minutes. Then 300
Slowly cool to ℃, and take out the optical glass element 22 from the outlet 23
Took out.

In the optical glass element 22 manufactured by such a process, the surface roughness (RMS) of the press-molded surface is an optical mirror surface of about 25Å, and bubbles, scratches,
Or, defects such as peeling marks are not recognized, and the surface accuracy is within 2 Newton rings and within 1/5 ass.
Its optical performance was extremely excellent.

Example 2 Using boron nitride as the first thermal processing jig,
It was processed into a convex shape with a radius of curvature of 45 mm. A concave optical surface 1 having a radius of curvature of 45 mm was formed using austenitic steel (SUS316) as a base material of the second heat processing jig. The optical surface 1 was further lapped with ultrafine diamond powder to make it a mirror surface having a surface roughness (RMS) of about 30Å in about 1 hour. On the surface of the heat processing jig that became a mirror surface,
Platinum-iridium-osmium alloy (Pt
-Ir-Os) thin film 2 was coated. Austenitic steel (SUS316) as a base material similar to the second heat processing jig
Is used to form a concave optical surface 1 having a radius of curvature of 150 mm, and a rhodium-gold-tungsten alloy (R
h-Au-W) thin film 2 was coated to obtain a press-molding die.

The molten glass 14 contains zirconia (ZrO ₂ ) 8% by weight, lanthanum oxide (La ₂ O ₃ ) 30% by weight, boric acid (B ₂ O ₃ ) 42% by weight, calcium oxide (CaO) 10% by weight, and the balance being trace amount. A lanthanum-based glass composed of the components was used. This glass 14
Nozzle 12 held at 950 ° C after melting at 00 ° C
From about 3 grams of molten glass 14 to 20 liters / minute of nitrogen gas, trichlorotrifluoroethane (C ₂ Cl ₃ F
₃ ) First heat processing jig 2 held in a molding machine in a halogenated hydrocarbon atmosphere mixed with gas at a rate of 1 liter / min.
4 was added dropwise. The first heat processing jig 24 is heated to 400 ° C. in advance, and immediately after the dropping, the second heat processing jig 16 is brought into contact with the molten glass 14 so that the second heat processing jig 24 receives the molten glass 14. Attached. The second heat processing jig 16 having the molten glass 14 attached thereto was inverted by the arm 25, and the molten glass 14 was replaced with the second heat processing jig 16 as shown in FIG. After being thermally deformed at 780 ° C. for 20 minutes by the second heat processing jig 16, it was press-molded by the press-molding die 20. The press molding conditions were a mold temperature of 680 ° C., a pressing pressure of 30 kg / cm ² , and a pressing time of 2 minutes. Then 40
The glass is gradually cooled to 0 ° C., and the optical glass element 2 is taken out from the outlet 23
2 was taken out.

In the optical glass element 22 manufactured by such a process, the surface roughness (RMS) of the press-molded surface is an optical mirror surface of about 20Å, and bubbles, scratches,
Or, defects such as peeling marks are not recognized, and the surface accuracy is within 2 Newton rings and within 1/5 ass.
Its optical performance was extremely excellent.

Example 3 Aluminum nitride was used as the first heat processing jig, and it was processed into a convex shape with a radius of curvature of 200 mm. A concave optical surface 1 having a radius of curvature of 200 mm was formed by using cermet (TiC-10Mo-9Ni) as a base material of the second heat processing jig. The optical surface 1 was further lapped with ultrafine diamond powder to make it a mirror surface having a surface roughness (RMS) of about 30Å in about 1 hour. Platinum-tantalum-rhenium alloy (Pt-Ta-R
The thin film 2 of e) was coated. Similar to the second heat processing jig, cermet (TiC-10Mo-9Ni) was used as a base material to form a concave optical surface 1 having a radius of curvature of 500 mm, and a platinum-tantalum-rhenium alloy (Pt) was formed by a sputtering method. -Ta
-Re) thin film 2 was coated to obtain a press molding die.

The molten glass 14 comprises 65 weight percent silica (SiO ₂ ), 9 weight percent potassium oxide (K ₂ O), 10 weight percent boric acid (B ₂ O ₃ ), 10 weight percent sodium oxide (Na ₂ O), and the balance being Borosilicate glass consisting of trace components was used.

After melting this glass at 1350 ° C., about 3 g of molten glass 14 was mixed from the nozzle 12 kept at 920 ° C. at a rate of 20 liters / minute of argon gas and 1 liter / minute of ethylene (C ₂ H ₄ ). It was dropped onto the first thermal processing jig 24 held in the molding machine in a hydrogen atmosphere. The first heat processing jig 24 is preheated to 550 ° C., and the molten glass 14 is brought into contact with the second heat processing jig 16 immediately after the dropping, so that the second heat processing jig 16 is exposed to the molten glass 14. Attached. The second heat processing jig 16 having the molten glass 14 attached thereto was inverted by the arm 25, and the molten glass 14 was replaced with the second heat processing jig 16 as shown in FIG. After being thermally deformed by the second heat processing jig 16 at 780 ° C. for 5 minutes, press molding was performed by the press molding die 20. Press molding conditions are mold temperature 680 ° C., press pressure 80 kg.
/ Cm ² , and the pressing time was 1 minute. After that, it was gradually cooled to 380 ° C., and the optical glass element 22 was taken out from the take-out port 23.

In the optical glass element 22 manufactured by such a process, the surface roughness (RMS) of the press-molded surface is an optical mirror surface of about 20Å, and bubbles, scratches,
Or, defects such as peeling marks are not recognized, and the surface accuracy is within 2 Newton rings and within 1/5 ass.
Its optical performance was extremely excellent.

Example 4 Martensite stainless steel (SUS420) was used as the first heat processing jig, and processed into a flat shape. Silicon was used as the base material of the second heat processing jig, and the radius of curvature was 55.
A concave optical surface 1 of mm was formed. The optical surface 1 was lapped with ultrafine diamond powder to obtain about 1
The surface had a surface roughness (RMS) of about 20Å. The thin film 2 of rhodium-gold-tungsten alloy (Rh-Au-W) was coated on the mirror-finished surface of the thermal processing jig by a sputtering method. Similar to the second heat processing jig, a concave optical surface 1 having a radius of curvature of 100 mm is formed by using silicon as a base material, and a thin film of rhodium-gold-tungsten alloy (Rh-Au-W) is formed by a sputtering method. 2 was coated to obtain a press molding die.

The molten glass 14 contains 52 weight percent silica (SiO ₂ ), 6 weight percent potassium oxide (K ₂ O), 35 weight percent lead oxide (PbO), and sodium oxide (N
a ₂ O) 5% by weight, the balance being a heavy flint glass consisting of trace components.

After melting this glass at 1250 ° C, from the nozzle 12 kept at 750 ° C, about 5 g of molten glass 14 was held in a molding machine in an atmosphere in which Helium glass was mixed at a rate of 20 liters / minute and carbon dioxide gas was 2 liters / minute. The first heat processing jig 24 was dropped. The first heat processing jig 24 was left without heating, the second heat processing jig 16 was brought into contact with the molten glass 14 immediately after dropping, and the molten glass 14 was attached to the second heat processing jig 16. . The second heat processing jig 16 having the molten glass 14 attached thereto was inverted by the arm 25, and the molten glass 14 was replaced with the second heat processing jig 16 as shown in FIG. After being thermally deformed at 610 ° C. for 5 minutes by the second heat processing jig 16, it was press-molded by the press-molding die 20. Press molding conditions are mold temperature 55
The temperature was 0 ° C., the pressure was 80 kg / cm ² , and the pressing time was 1 minute. After that, it was gradually cooled to 380 ° C., and the optical glass element 22 was taken out from the take-out port 23.

In the optical glass element 22 manufactured by such a process, the surface roughness (RMS) of the press-molded surface is an optical mirror surface of about 20Å, and bubbles, scratches,
Or, defects such as peeling marks are not recognized, and the surface accuracy is within 2 Newton rings and within 1/5 ass.
Its optical performance was extremely excellent.

The method for producing an optical glass element of the present invention is a step of producing a glass gob by receiving molten glass in a non-oxidizing atmosphere with a first heat processing jig that does not have a shape similar to that of the desired optical glass element. A step of inverting and replacing the glass gob and the second heat processing jig in a state where the glass gob is bonded to a second heat processing jig having a glass element and an approximate shape;
Manufacture of an optical glass element including a step of producing an optical glass molded body by the surface tension of the glass gob heat-softened by a second heat processing jig, and a step of heating and pressing the optical glass molded body with a press molding die. This method is characterized in that the molding atmosphere, the optical glass composition, the thin film composition for coating the thermal processing jig, the temperature and time of thermal deformation, the shape of the optical glass molded body, etc. It is not limited to the example.

Effects of the Invention As described above, the method for producing an optical glass element of the present invention, in order to remove the wrinkle-like defects on the surface of the glass gob that is in contact with the heat processing jig, the molten glass is approximated to the desired optical glass element. After receiving with the first heat processing jig, contact the smooth surface of the glass gob with the desired optical glass element and the second heat processing jig of similar shape, and use the glass gob as the second heat processing jig. Attach it. With the glass cob attached to the second thermal processing jig, reverse the second thermal processing jig to stably replace the glass gob with the second thermal processing jig from the first thermal processing jig, The glass gob having a wrinkled surface facing upward is largely deformed by the surface tension of the glass by the heated second heat processing jig. Furthermore, the optical glass element having no surface defects can be manufactured by subjecting this optical glass molded article to heat and pressure molding with a press molding die.

That is, the present invention enables mass production of highly accurate optical glass elements, and has a remarkable effect in improving productivity and reducing manufacturing cost.

[Brief description of drawings]

FIG. 1 (a) is an explanatory view of a first thermal processing jig for explaining the present invention, and FIG. 1 (b) is an explanatory view of a second thermal processing jig for explaining the present invention. FIG. 1 (c) is a sectional view of a press-molding die, and FIG. 2 is a sectional view of an embodiment of the present invention showing an optical glass element manufacturing apparatus. 1 ... Optical surface, 2 ... Thin film, 10 ... Glass melting furnace, 1
1 ... Heating heater, 12 ... Nozzle, 13 ... Nozzle heating heater, 14 ... Molten glass, 15 ... Heating heater,
16 ... Second heat processing jig, 17 ... Gas inlet, 18 ...
… Optical glass molding, 19 …… Press cylinder, 20…
... press molding die, 21 ... conveyor, 22 ... optical glass element, 23 ... outlet, 24 ... first heat processing jig, 25 ... arm.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadataka Yonemoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A step of producing a glass gob by receiving molten glass with a first heat processing jig which is not in a shape similar to that of a desired optical glass element in a non-oxidizing atmosphere, A step of inverting and replacing the glass gob and the second heat processing jig in a state where the glass gob is adhered to the second heat processing jig, the surface tension of the glass gob thermally softened by the second heat processing jig And a step of heating and pressing the optical glass molded body with a press-molding die to produce an optical glass molded body. 2. The method for producing an optical glass element according to claim 1, wherein the first heat processing jig has poor wettability with the molten glass. 3. The second heat-processing jig and press-molding die are processed into a desired shape and optical surface and are covered with a thin film which has good wettability with molten glass and is chemically stable. (1) The method for producing an optical glass element described in (1). 4. The thin film is a noble metal, tungsten, tantalum,
The method for producing an optical glass element according to claim (3), which is a simple substance of rhenium or hafnium or an alloy thereof.